Our goals are to acquire simultaneous two-photon images of ALA-induced PpIX and NADH autofluorescence using several well-defined cell lines and normal and tumor tissues of the balb-c mouse. While much is known regarding the heme biosynthesis pathway, recent steady-state fluorescence polarization studies indicate the possibility that the site of PpIX formation may differ in normal and tumor tissues. We propose to address this issue using multiphoton excited NADH autofluorescence and possibly other extrinsic mitochondrial indicators to observe the localization of ALA-induced PpIX in the samples cited above.